A century from now, London could be a backwater too. The city faces its own set of threats. Most pressingly, few people can afford to raise families there any more. London may become a gated playground for the super-rich. However, there’s an alternative scenario in which the place just keeps getting more successful. Already the contours are emerging of a future London: the city as a giant drop-in office for millions of occasional workers who live far away, often in other countries. A ring of satellite cities ranging from Manchester to Rotterdam would turn into a new set of suburbs for London.

The problem London needs to solve, says Andrew Adonis, Londoner, Labour peer and writer, is, “Housing, housing, housing.” What’s happening in London’s housing market can no longer be described as gentrification. That was the ousting of the city’s working class and bohemians. Now many upper-middle-class people are being forced out too. Michel Mossessian, a French architect in London whose firm employs lots of nationalities, sees something of a “seven-year cycle”: people work for seven years in London but then often leave once they have children. It’s not just that the average three-bedroom home in London now costs £1.1m, according to Home.co.uk. It’s also that London’s state schools — despite vast recent improvements — will probably never meet the standards of the world’s most aspirational parents. Simply being the best state schools in England isn’t enough.

The solution: London needs to adopt satellite cities that can house a new tribe of “occasional Londoners”. In the Victorian era, the coming of the Tube and trains allowed London workers to move to suburbs. Soon high-speed trains will allow occasional London workers to live hundreds of miles away, around Britain or abroad.

The UK currently has just 68 miles of high-speed rail line, from London to the Channel tunnel. But when the High Speed 2 line opens over the next 20 years, Birmingham will be 49 minutes from London, and Manchester just over an hour. “That’s hugely exciting,” says Adonis.

Already cities such as Paris, Lille and Brussels are joining the Londonsphere. I live in Paris. Sometimes I drop the kids off at school at 8.30am and later that morning meet someone for coffee near King’s Cross. I will probably never live in London again but I don’t mind. London and Paris are now perhaps the two most connected cross-border metropoles in history, an unprecedentedly creative network with trains carrying ideas back and forth. But I also know people who live in Germany or Spain and work in London a couple of days a week.

London companies will need to strike a new deal with occasional workers: live somewhere else but drop in on us regularly. The companies won’t need to pay these people the “London premium” on salaries, or rent lots of expensive office space. The trains that carry occasional Londoners will themselves act as de facto offices: the Eurostar, French TGVs and Thalys, in utter contrast to suburban commuting trains, guarantee you a seat and a fold-out table. Sometimes the WiFi even works. Trains also free you from the Dilbertian timewasting of office life: the colleagues loafing around your desk grumbling about the commute, the boss or José Mourinho.

Occasional Londoners can buy a family home in Lille or Rotterdam, spend £15,000 a year travelling to London for work and fun for 40 years and still be better off than if they’d spent that £1.1m on a house in London. And they won’t have to school their kids there. Homeshare websites such as Airbnb are solving London’s shortage of affordable hotel rooms while allowing the city’s large population of slacker-heirs to monetise their only asset.

In this scenario, London becomes not Vienna but Tokyo. Specifically: Greater Tokyo, brilliantly served by bullet trains, and today the biggest metropolitan area in history with about 36 million inhabitants. That’s a nice target for the Londonsphere. London would then be the capital of a new informal empire spanning several countries.

London as giant drop-in office could be a reality within 20 years. That may seem improbable. But just over 20 years ago, nobody imagined that this grey city with 1960s Tube trains, separated from the continent only by a long traffic jam to Heathrow and then hours of dead time, could ever exert such attraction that a three-bedroom house would cost £1.1m.